The Two October Self Assessment Deadlines You Need to Know

This guidance is for Self Assessment taxpayers who are unsure what happens if one or both October deadlines are missed, and how those deadlines affect later penalties and filing options.

October is a critical month for Self Assessment because it includes more than one deadline. Missing either can have knock-on effects, even if the main January deadline has not yet passed, particularly for those seeking self assessment advice in London.

Key October Deadlines for Self-Assessment Paper Filers

The deadline for submitting paper self-assessment tax returns for the 2023-24 tax year is 31 October 2024. Late submission of a self-assessment return will generate a £100 late filing penalty. The penalty usually applies even if there is no liability or if any tax due is paid in full by 31 January 2025.

Daily penalties of £10 per day will also take effect if the tax return is still outstanding three months after the filing date up to a maximum of £900. Additional higher penalties will be incurred if the return remains outstanding after six and twelve months.

We would recommend that anyone still submitting paper tax returns consider the benefits of submitting the returns electronically. This would allow for an additional three months until 31 January 2025 in which to submit a return.

In addition, you must inform HMRC by 5 October 2024 if you need to complete a tax return for the 2023-24 tax year and have not done so before. Failure to do so could result in a fine.

What Happens If You Miss One or Both October Deadlines

If you fail to notify HMRC by 5 October when required, HMRC may issue a notice to file later than expected, increasing the risk of missed deadlines and penalties further down the line.

If you miss the 31 October paper filing deadline, you lose the ability to file a paper return and must submit your return online instead. Filing the return late can still trigger an automatic £100 late filing penalty, even if no tax is due.

These October deadlines also affect how smoothly your Self Assessment record is set up for the year. Problems at this stage often lead to avoidable penalties later. Which is why many people choose to speak to a tax consultant in London early on.

In Practice – Why October Deadlines Cause Problems

In practice, we often see taxpayers focus entirely on the January deadline and overlook the importance of October. Confusion between the 5 October notification deadline and the 31 October paper filing deadline is one of the most common causes of early Self Assessment issues.

For practical assistance, experienced accountants in Farringdon work with taxpayers across nearby areas such as Chancery Lane and Finsbury when Self Assessment deadlines have been missed and penalties are in issue. At CIGMA Accounting, we can help you understand the consequences of missing the October deadline, assess what action is still required, and advise on the most appropriate next steps to take with HMRC.

Review What Happens If You Miss an October Self Assessment Deadline

If you missed one or both October deadlines, the consequences are not always immediate but can still affect your tax position. A short review can help confirm what applies to you and what action may reduce further penalties.